Ultrasonic humidifier



FIG. 1 is a perspective view of an ultrasonic humidifier showing my new design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a left side elevation view thereof;

FIG. 4 is a right side elevation view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a rear elevation view thereof; and

FIG. 7 is a bottom plan view. 

The ornamental design for an ultrasonic humidifier, as shown. 